phasing/comb filtering issue w/ audio suite?

[sonalma]

I began a mix this morning as I usually do. I generally use rtas plugins to find the sound I want, save the settings as a preset then apply audio suite to the file to save cpu power because I have a very old mac. After working the overheads and kik drum in this manner, I applied audio suite eq and compression to the snare. I have worked this way many times with no problems. Today however, I can hear the snare with some kind of flanging/phase everytime it hits. I tried nudging it to align it with the snare on the overhead tracks but same problem. Anybody have any ideas on why this is happening? Thanks.